This invention relates to a method of withdrawing particulate material from a centrifugal crusher after the particulate material has stayed for a while in a crushing chamber of the centrifugal crusher wherein material to be crushed, such as mineral ore, is fed to a rotor rotating at high speed and is thrown by centrifugal force in a tangential direction against the surface of a dead-bed constituted by particulate material produced by crushing the material fed to the rotor and stacked in a heap in the crushing chamber around the rotor, and a centrifugal crusher of the type suitable for carrying the method into practice.
In a centrifugal crusher for crushing material thrown out of the rotor by centrifugal forces, it has hitherto been usual practice to use a rebound plate of high rigidity against which the material to be crushed is thrown by centrifugal forces. This type of centrifugal crusher of the prior art has suffered the disadvantage that wear is readily caused on the rebound plate because of high impact applied thereto by the material to be crushed. Proposals have been made in recent years to use a centrifugal crusher of the type in which a dead-bed constituted by particulate material produced by crushing material fed to the rotor is used in place of the rebound plate. This type of centrifugal crusher is free from the aforesaid disdvantage of the centrifugal crusher using a rebound plate and has a high practical value. However, the centrifugal crusher now available which relies on a dead-bed is not without disadvantages. One of them is that the material to be crushed impinges on the dead-bed and is crushed thereby into particulate material which scatters and moves downwardly to be released from the crusher. The kinetic energy possessed by the material to be crushed which is thrown out the rotor by centrifugal force should be used for crushing the material itself and for crushing the particulate material constituting the dead-bed into still smaller particles. However, in the centrifugal crusher using the dead-bed which is non available, the energy directed against the dead-bed is wasted because it is absorbed by the dead-bed, without contributing to further crushing of the particulate material of the dead-bed into smaller particles.